This invention relates to a solenoid operated fluid control valve and particularly to one adapted for use in motor vehicles.
Modern motor vehicles employ complex fluid control system such as the pneumatically operated portions of the vehicle's emission control system. For such systems, it is frequently desirable to employ valves which switch or control the flow of fluid using low voltage electrical signals. Such valves are frequently used to control vacuum signals which are used to operate exhaust gas recirculation (EGR) systems or to control functions of a vehicle's heater, ventilation and air conditioning systems. Numerous designs for such solenoid operated valve devices are presently known. This invention seeks to provide a number of improvements in the design, operation, fabrication and calibration of such valve assemblies.
In solenoid designs using a "C" frame which provides a conduction path for a portion of the closed magnetic circuit of the device, it is ordinarily desirable to position the frame member such that it is in direct contact with the metal pole piece and/or other components of the magnetic circuit. These inventors have, however, found that direct contact between the "C" frame member and pole piece of a solenoid operated valve can cause vibrations to be transmitted to the solenoid structure which results in the emission of high decibel audible sounds during actuation. Such noise can constitute an annoyance to the vehicle occupants particularly if the device is installed in a motor vehicle in close proximity to the occupant compartment. Accordingly, it is an object of this invention to provide a solenoid operated valve device which features low actuation sound levels.
Modern manufacturing techniques rely heavily on automated assembly as a means of reducing piece price. Such efforts toward automation have been particularly evident in the domestic automobile industry. In the past, great difficulty has been encountered in winding coils for solenoid devices using entirely automated processes. Typically, it is necessary to employ manual operations to terminate the ends of the solenoid coil. It is, accordingly, another object of this invention to provide a coil assembly which can be fabricated employing automated machinery.
For solenoid operated fluid control valves to operate in accordance with motor vehicle manufacturer's rigid specifications, it is necessary to provide highly accurate relationships amongst the various components of the device. One approach toward achieving such accuracy is to provide highly precision components having narrow dimensional tolerance ranges. Although devices constructed in such a manner operate satisfactorily, they are costly due to the required dimensional precision of the components. Another approach is to provide a means for calibrating the components such that the article is tolerant to component dimensional variations. If a cost effective calibration process is available, this approach can provide cost savings. It is, accordingly, yet another object of this invention to provide a solenoid operated valve incorporating a method for calibrating the system to precise dimensional relationships without requiring critically dimensioned components.